Oil Weights for Summer Use

The Old Rules Don’t Always Apply

Summer means hot weather and if you are following your grandfather’s footsteps you are probably reaching for heavier weight oil to protect your car, truck, ATV, UTV or anything else requiring a four-stroke lubricant. Lubricants are naturally thinner in hotter weather, so logic would tell us heavier weight oil is needed to provide the same engine protection you get from thinner oil in cooler weather. This logic holds true in some cases, but not for the reasons you would think.

Since your Grandfather’s time, EPA fuel economy mandates have motivated automobile manufacturers and oil formulary scientists to adopt lower engine oil viscosity grades. Fuel economy is a major consideration in much of the engineering that goes into new cars. The new engine lubricants of today are designed to protect automobile engines over a wide temperature range, often with lower viscosity schemes. One of the major contributors to increased fuel economy is achieved through the lowering of viscous drag that heavier engine oils can create. Manufacturers have learned they can gain a fuel mileage advantage with thinner oil and protect their engines at the same time. Honda has capitalized on this by using 0W-20 oil and more recently have received API certification for its 0W-16 oil. Thinner oils have arguably played a bigger role in reducing EPA fuel mileage numbers than other technologies such as direct injection or CVT transmissions (comparing like models and gross vehicle weights). Automobile manufacturers go to great lengths to assure that the recommended lubricant is of the proper viscosity grade to optimize both fuel economy and engine protection. There is really no need to go outside of the recommended viscosity grade to protect your engine when it gets hot.

Turning to heavier weight oil is still important when it comes to ATVs, UTVs and other off-road vehicles (ORVs). One of the main reasons is fuel dilution which thins the oil. Typical fuel dilution in passenger cars is under 1 percent. Fuel dilution in recreational vehicles can be as high as 7 percent with 3 to 5 percent being quite common. Using the manufacturer’s recommended lubricant assures that the engine will be protected in the face of high fuel dilution. ORVs and many motorcycles also run at higher RPMs (8,000 or more) and use a common sump for the engine and transmission which can introduce the oil to a lot more heat and shear forces, all of which require heavier weight oil to provide proper lubrication. Finally, ORVs aren’t built for mileage, they are built for work or play and they often see intermittent use putting even more responsibility on the oil to stand up to moisture, fuel dilution and other contaminants.

While heat can be a real danger to internal combustion engines, modern automobiles have been engineered to run optimally on thinner oils no matter what the ambient temperature. Though they are designed and driven much differently than automobiles, ORVs can typically get by on an all-season oil as well but they are typically heavier in viscosity due to the factors listed above. Recently, manufacturers of ATVs have put more emphasis on special lubricants designed for extreme summer or hot weather use. If you work your ATV or other ORV hard by using it to do such things as pull implements, race or use it in hot climates, using these special lubricants will assure you are doing all you can to protect your investment.